Polychloropropane is important as a raw material or an intermediate for producing various products such as agricultural chemicals, medicinal products and freon substitutes. For example, trichloroallyl diisopropylthiocarbamate which is useful as a herbicide can be produced from 1,1,1,2,3-pentachloropropane as a starting material through 1,1,2,3-tetrachloropropene.
As a method of producing this polychloropropane, there is known a three-stage reaction consisting of a first reaction for obtaining chloropropane by adding carbon tetrachloride to an unsaturated compound having 2 carbon atoms (nonsubstituted or chlorine-substituted ethylene), a second reaction for obtaining chloropropene by dehydrochlorinating the chloropropane and a third reaction for obtaining chloropropane of interest by further adding chlorine to the chloropropene. As the second reaction and the third reaction particularly relevant to the present invention out of these reactions, for example, U.S. Pat. No. 4,650,914 (document 1) discloses an example in which 1,1,1,2,3-pentachloropropane is obtained by causing an alkaline aqueous solution to act on 1,1,1,3-tetrachloropropane to carry out a dehydrochlorination reaction so as to obtain a mixture of 1,1,3-trichloropropene and 3,3,3-trichloropropene, separating a water phase from the mixture and chlorinating the obtained product by using chlorine.
As for the dehydrochlorination reaction as the second reaction, JP-A 49-66613 (document 2) discloses a method in which the reaction is carried out at a high temperature in the presence of iron chloride as a catalyst.
Further, as a method in which the above second reaction and the above third reaction are carried out in a single step, US Patent Publication 2009/216055 (document 3) discloses a method of obtaining 1,1,1,2,3-pentachloropropane at a stretch by blowing a chlorine gas into 1,1,1,3-tetrachloropropane at a high temperature in the presence of iron chloride as a catalyst.
When the polychloropropane is to be produced by the methods of the above patent documents 1 and 2, the reactions of the two steps must be carried out under completely different conditions, whereby a plurality of reactors are required and the reactions take long, which is uneconomical. When the polychloropropane is to be produced by the method of the patent document 3, the above problems are eliminated due to a single-step reaction. However, a high-temperature reaction is required and the selectivity of a product of interest is unsatisfactory, whereby there is large room for improvement.
Meanwhile, highly chlorinated polychloropropene such as 1,1,2,3-tetrachloropropene is important as a raw material or an intermediate for producing various products such as medicinal and agricultural products and freon substitutes (for example, the above document 3, U.S. Pat. No. 5,659,093 and US Patent Publication 2009/240090).
As one of the methods of producing this polychloropropene, there is known a method in which high-order chlorinated propane having at least one hydrogen atom is dehydrochlorinated to produce a double bond. As for this dehydrochlorination, there are known a method in which high-order chlorinated propane is brought into contact with an alkaline aqueous solution such as a sodium hydroxide aqueous solution in the presence of a phase transfer catalyst (for example, JP-A 2010-229047 and JP-A 2010-229092) and a method in which high-order chlorinated propane is heated in the presence of ferric chloride (for example, the above document 3 and U.S. Pat. No. 3,732,322).
However, when polychloropropene is produced by bringing high-order chlorinated propane into contact with an alkaline aqueous solution, a large amount of alkaline liquid waste which is produced after the reaction must be disposed of. When ferric chloride is used, liquid waste to be disposed of is not substantially produced but there is large room for improvement in terms of reaction conversion and the selectivity of a product of interest.